Software Events are things that happened in the system that other components might be interested in knowing about. PHP developers are generally not used to working with Events, which are not a feature in the language. However, it's more common to see how new frameworks and libraries embrace them to provide new ways of decoupling, reusing, and speeding up code.

Domain Events are Events related to Domain changes. Domain Events are things that happen in our Domain that Domain Experts care about.

In Domain-Driven Design, Domain Events are fundamental building blocks that help:

• Communicate with other Bounded Contexts.
• Improve performance and scalability, pushing for eventual consistency.
• Serve as historical checkpoints.

Domain Events represent the essence of asynchronous communication. For more on this topic, we recommend the book Enterprise Integration Patterns:  Designing, Building, and Deploying Messaging Solutions by Gregor Hohpe and Bobby Woolf.